The Display Module, also called Operating Panel, is mounted to the side of the Highway Traffic Director or Preferred Access Expander. It can be removed and secured elsewhere as long as it's within the 200 Feet signal limit.

The HTD receives error reports from a Preferred Access Device(PAD). When a box fails multiple times and surpasses the minimum number of errors allowed, the PAD sends a signal to the HTD Operating Panel which then switches highways to try and remove errors.

Panel has an Alarm LED which when lit means the HTD has not polled within the last 30ms. This is a real time alarm which means LED can reset itself if no alarm is present again when it polls. The backup LED is lit when the selected hiway fails.